Talking about the model airplane lithium battery

by:CTECHi     2021-07-31

The battery is the heart of the model aircraft. Motors, steering gears, and receivers all rely on battery drive. The selection of the battery depends not only on the battery life. Discharge voltage, current, energy storage density, and even external dimensions are all factors that need to be considered. First, let’s talk about the basic parameters of model aircraft batteries. Take the 2800mAh25C22.2V battery in the above figure as an example. 2800mAh means that the battery can discharge up to 2800mA for one hour. But in general, it is concluded in destructive experiments that the battery will consume about 50% of the power from 4.20V to 3.80V; when it is 2.75V, the consumption reaches 100%, but the battery is basically scrapped after discharge. The lithium battery capacity on the market is distributed from 50mAh to 10000mAh. Lithium battery capacity is directly related to the weight of the battery. This involves the balance between battery life and weight loss. Next, let's talk about the discharge rate of the battery. 25C refers to the nominal current (how many milliamperes per milliampere hour, in the example is 2800mAh) as the unit one, multiply the C number to get the maximum discharge current of the battery (in the example, 2.8A *25u003d70A). The C number marked on the battery generally has a margin. Continuous discharge at this rate generally does not cause safety problems, so it is called continuous discharge rate. And another parameter, the peak discharge rate, refers to the battery can be discharged at the changed rate for a short time (generally no more than 10 seconds). Discharging with a current exceeding the safe discharge rate may cause safety accidents such as battery swelling, fire, and explosion. Under normal circumstances, it is recommended that the continuous discharge current of the battery is slightly higher than the overall current consumption of the model airplane (including the power unit, transmission and receiving device). The discharge rate of charge and discharge should not be confused. Generally, the charge rate is lower than the discharge rate. When using an advanced charger, be careful not to set the charging current higher than the maximum charging current calibrated for the battery. According to my habit, I usually charge at a rate of 1-2C. In addition, as the battery is used, the internal resistance of the battery will gradually increase. This will affect the maximum discharge rate of the battery. Let's talk about the voltage of the battery. In the example, 22.2V is the nominal voltage of the model airplane battery. The nominal voltage of a single-cell lithium battery is 3.7V, so divide 22.2 by 3.7 to get 6. The lithium battery is a series of six 3.7V cells (that is, a 6S battery). The full-charge voltage of aeromodelling batteries is generally 4.2V (high-voltage lithium batteries are now available on the market, with a full-charge voltage of 4.35V, which has greater energy storage, greater voltage and stronger power than 4.2V lithium batteries). The storage voltage of aeromodelling battery is generally 3.85V. At this time, the battery is in a relatively safe state and is not prone to swelling and explosion safety accidents. The discharge safety voltage of the battery (lower than this voltage is likely to cause battery capacity loss and battery swelling problems) is generally 3.60V, and the alarm voltage during airplane flight can also be set at 3.60V. 2.75V is the discharging termination voltage of the lithium battery. At this time, the battery is fully discharged and the battery capacity is greatly depleted. At this time, charging will occur swelling (gas is generated inside, but if the air pressure is too high, it may explode). Due to the physical and chemical properties of lithium batteries, the voltage will continue to change if the charge and discharge are stopped after high-rate charge and discharge. This phenomenon is called virtual electricity. According to experience, if 3.6V is used as the alarm voltage and the battery is removed after the flight, the voltage will rise after a period of time. this is normal phenomenon. Lithium batteries ranging from 1S to 12S are available on the market. Generally speaking, KT board machines are mostly 3S. With the same power, the higher the voltage, the smaller the current and the smaller the heat generation. But also consider the limitation of the maximum voltage of the ESC motor and the receiver. Let’s talk about the structure and connectors of the lithium battery. The core of a lithium battery is a packaged battery cell. The batteries are connected in series. There are generally two output terminals, one is the power line, usually a thick silicone line, which is used to supply power to the model aircraft power equipment. There are many kinds of connectors for the power line, the T plug is the cheapest and the most widely used, but the safety is worrying. JST connectors are often used in light aircraft such as F3P. XT60 can safely power small and medium current model airplanes. XT150 is generally used in high-current equipment such as helicopters. In addition, the other wire on the lithium battery is thinner, called a balance head, and is directly connected to a battery cell. It is generally used for charging and voltage monitoring. Safety issues about lithium batteries: swelling, simple swelling will not cause safety problems . But if the air pressure is too high, you can consider poke holes in the battery skin to discharge the gas, and then seal the small holes. However, there are certain safety hazards in doing so. Excessively swollen batteries are recommended to be eliminated. Two: leakage. Under normal circumstances, liquid leakage will not cause safety accidents. But liquids are often corrosive. In addition, the battery cell voltage after leakage will gradually drop to 0, so consider dismantling the battery holder to reduce the number of electric chips. Three: Impact deformation. If the battery does not leak or explode after the impact, the battery can still be used normally. Four: short circuit. A short-circuited battery will explode in a short time

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